Method of separating fatty acids from rosin acids of tall oil



Patented Jan. 16, 1951 UNITED STATES iitTENT OFFICE METHOD OF SEPARATIN G FATTY ACIDS FROM ROSIN ACIDS OF TALL OIL N Drawing. Application November 9, 1946, Serial No. 708,930

7 Claims.

Thi invention relate to a method of separating tall oil into a fatty acid fraction and a rosin acid adduct fraction.

It is known that maleic anhydride and compounds such as quinone, anthraquinone, allyl chloride, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, aconitic acid, acrylic acid, acrylonitrile, crotonic acid, isocrotonic acid, methacrylic acid, tiglic acid, acetylene dicarboxylic methyl ester, vinyl acetate, and esters of maleic and fumaric acids, for example dimethyl maleate and dimethyl fumarate, will add to other compounds, such as rosin acids which contain a conjugated system of double bonds. The products of these reactions are called adducts.

This invention has for its object to provide a method whereby the separation of tall oil into fatty acid and rosin acid adduct fractions may be accomplished in a high-vacuum unobstructedpath still. Another object is to provide a method whereby the fatty acids in tall oil may be freed of resinous material. A further object is to provide a method whereby the rosin acid in tall oil may be converted into compounds having a higher boiling point. Another object is to provide a method whereby the rosin acids in tall oil may be converted into compounds useful in the manufacture of alkyd resins. Another object is to improve the state of the art. otheriobjects will appear hereinafter.

These and other objects are accomplished by our invention which includes reacting tall oil with a compound which will form adducts with the rosin acid fraction and subjecting the mixture to high-vacuum unobstructed-path distillation to separate the fatty acid fraction as dis tillate.

In the following description we have set forth several of the preferred embodiments of our invention but it is understood that these are given by way of illustration and not in limitation thereof.

Tall oil is usually marketed in partially purified form. Our invention applies to this form as Well as crude tall oil. As long as rosin acids and fatty acids are present our invention applies irrespectiveof the degree to which the oil has been purified. Tall oil may be reacted with any dienophile to form adducts of the rosin acids and the dienophile. A dienophile is a compound with at least one activating group, for example, chlorine or a hydroxyl group, and at least one double bond. Examples of dienophiles are maleic anhydride, quinone, anthraquinone, allyl chloride, maleic acid, itaconic acid, aconitic acid, acrylic acid, acrylonitrile, crotonic acid, isocrotonic acid, methacrylic acid, tiglic acid, acetylene dicarboxylic methyl ester, vinyl acetate, and esters of maleic and fumaric acids, for example dimethyl maleate and dimethyl fumarate.

Most of the above compounds react with the rosin acids of tall oil to give adducts of molecular weight substantially higher than the original rosin acids. These high-boiling, relatively nonvolatile adducts promote sharp separation of the fatty acid fraction in a high-vacuum unobstructed-path still.

Treatment of abietic acid with maleic anhydride will illustrate the application of our invention. Abietic acid is in equilibrium with an isomer, l-pimaric acid. At low temperatures abietic acid predominates. Higher temperatures, for example over 0., promote an equilibrium shift in favor of l-pimaric acid. It is the lpimaric isomer which forms adducts with dienophiles. Formation of an adduct of l-pimaric acid and maleic anhydride results in further production of l-pimaric acid until the reaction is complete. In the high-vacuum unobstructedpath still the tall oil fatty acids will separate more readily from the adduct than from unmodified abietic acid.

Most of the adducts are high-melting solids, a portion of which will crystallize out of the reaction mixture upon cooling. These may be separated and the remaining liquid subjected to dis titllation in the high-vacuum unobstructed-path s ill.

The dienophile, e. g. maleic anhydride, is reacted with the tall oil for a period of about 3 to 20 hours at temperatures of about 150 C. to 210 C. We prefer to use the higher temperature range, e. g. 200 0., as the reaction period is thereby lowered to about three hours. The quantity of dienophile used is equimolar to the quantity of rosin acids present. At the end of the reaction period the mixture is cooled. Usually a portion of the adduct precipitates upon cooling and sharper ultimate separation may be obtained if this precipitated adduct is removed by filtration. This step may be omitted. In either case the mixture is next subjected to distillation in a highvacuum unobstructed-path still. The first fraction begins to distill at about 90 0. and so microns pressure. Subsequent fractions are preferably taken up to a temperature of C. and down to a pressure of 5 microns. The bulk of the fatty acids are distilled within the temperature range of 90-100 C. and pressure range of 5-10 microns.

Example 1 13.13 kg. of tall oil containing 5.45 kg. of rosin acids were treated with 1.84 kg. of maleic an hydride at 150 C. for 20 hours. After cooling, the mixture was heated again to 100 C. Whereupon the crystalline adduct was separated and filtered off. Yield of adduct: 40 per cent of that calculated. The filtrate was distilled in the centrifugal molecular still giving out 88 per cent yield of fatty acids. The remainder of the adduct was in the residue.

P Mgl. Per PcrTC cnlt or Tempercnt of ota ig Cent ature, Fatty Fatty Cut C. Acid A cids in Content Fraction 67. 3 i s i 3. 6 93 93. S 30 6. ll. 1 92 95. S 9 20. 0 7. a 90 94. 2 0 13. 4 7. 7 97 91. 7 5 13. 6 5. 3 9?.- 90. 7 4 9. 7 5. 5 100 86. 7 (i 9.7 G. 8 l 18 72. O 8 V 0 3. S 113 59. l 5 5. 0 O. B 138 50. 8 7 O. 9

The first seven fractions, either singly or as a composite, are clear, light-colored oils which are suitable as industrial fatty acids for use in alkyd resins, soaps, lubricating greases, surface ctive agents, polishing and bufiing compounds, candles, cosmetics, driers, and rubber goods. The eighth and ninth fractions, being intermediate fractions and resembling the original charge in composition, can be recycled through the still. fhe residue, which consists of the rosin acid adduct and the unsaponifiable material of the tall oil, can be separated into acidic and neutral compounds.

Example 2 500 g. of tall oil, containing 0.687 mole of rosin acids, were heated with 90 g. of itaconic acid at 190 C. for 4 hours in a three-neck flask which was equipped with an air stirrer, an air condenser, and a thermometer. After cooling, the reaction mixture was distilled in a molecular still.

Example 3 500 g. of tall oil, containing 0.687 mole of rosin acids, were heated with 120 g. of aconitic acid at 190 C. for 4 hours in a three-neck flask which was equipped with an air stirrer, an air condenser, and a thermometer. After cooling, the reaction mixture was distilled in a molecular still.

What we claim is:

l. A process of treating tall oil containing fatty acids and rosin acids which comprises converting said rosin acids to rosin acid adducts having boiling points substantially higher than said rosin acids while leaving a fatty acid fraction as such by reacting said tall oil with a dienophile at a temperature not higher than 210 C. and

thereafter separating said fatty acid fraction by a distilling operation.

2. A process of treating tall oil containing fatty acids and rosin acids which comprises converting said rosin acid to high-melting solid rosin acid adducts while leaving a fatty acid fraction such by reacting said tall oil with a dienophile at a temperature not higher than 210 0., precipitating and removing a substantial amount of said adducts, and thereafter separating said fatty acid fraction by a distilling operation.

3. A process of treating tall oil containing fatty acids and rosin acids which comprises converting said rosin acids to rosin acid adducts having boiling points substantialy higher than said rosin acids while leaving a fatty acid fraction as such by reacting said tall oil with maleic anhydride at a temperature of -210 C., and thereafter separating said fatty acid fraction by a distilling operation.

4. A process of treating tall oil containing fatty acids and rosin acids which comprises converting said rosin acids to high-melting solid rosin acid adducts while leaving a fatty acid fraction as such, said converting being effected by admixing said tall oil with maleic anhydride and condensing rosin acids present in said tall oil with said maleic anhydride at a temperature of 150-210 C., precipitating and removing a substantial amount of said adducts, and thereafter separating said fatty acid fraction by a distilling operation.

5. A process of treating tall oil containing fatty acids and rosin acids which comprises admixing tall oil and a dienophile, condensing rosin acids present in said tall oil with said dienophile forming rosin acid adducts having boiling points substantially higher than said rosin acids by reacting said rosin acids and said dienophile at a temperature not higher than 210 C. leaving said fatty acids in uncondensed form, and thereafter separating said fatty acids from said rosin acid adducts by vacuum distilling said fatty acids therefrom.

6. A process of treating tall oil containing fatty acid and rosin acids which comprises converting said rosin acids to higher melting rosin acid adducts by heating said tall oil in admixture with maleic anhydride at a temperature of 150-210 C., said temperature being insufficient to cause substantial condensation of said maleic anhydride with said fatty acids, and thereafter subjecting the resulting mixture of said fatty acids and said rosin acid adducts to highvacuum unobstructed-path distillation effective to distill said fatty acids from said mixture.

7. A process of treating tall oil containing fatty acids and rosin acids which comprises converting said rosin acids to rosin acid adducts having boiling points substantially higher than said rosin acids while leaving an unreacted fatty acid fraction, said converting comprising reacting said tall oil with a dienophilic compound at a temperature of 150-210 (3., said dienophilic compound being characterized by having a carbonylic group joined to an olefinic carbon atom, and thereafter separating said fatty acid fraction by a distilling operation.

SAMUEL D. KOONCE. EDMOND S. PERRY.

GEES @HTED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,188,886 Clocker Jan. 38, 1940 2,269,243 Baxter et al Jan. 6, 1942 2,312,731 Salathiel Mar. 2, 1943 2,312,732 Salathiel Mar. 2, 1943 2322,17? Blair June 17, 1947 FOREIGN PATENTS Number Country Date 355,281 Great Britain Feb. 1931 

1. A PROCESS OF TREATING TALL OIL CONTAINING FATTY ACIDS AND ROSIN ACIDS WHICH COMPRISES CONVERTING SAID ROSIN ACIDS TO ROSIN ACID ADDUCTS HAVING BOILING POINTS SUBSTANTIALLY HIGHER THAN SAID ROSIN ACIDS WHILE LEAVING A FATTY ACID FRACTION AS SUCH BY REACTING SAID TALL OIL WITH A DIENOPHILE AT A TEMPERATURE NOT HIGHER THAN 120* C. AND THEREAFTER SEPARATING SAID FATTY ACID FRACTION BY A DISTILLING OPERATION. 